346 
Merlsm and Sex in " Spinax Niger'" 
are bronght about by random excision or interpolation of segments. The various 
positions of the different characters studied (e.g. spines &c.) are probably due to 
homoeosis, and the reality of this factor is brought out by a study of the correlations 
with one another of the various characters chosen. 
(5) The study of the variations of the girdle canals supports the view that 
the different positions of the pelvic girdle are brought about by a process of 
homoeosis as opposed to one of excalation or intercalation. 
(6) Certain discrepancies in the correlation values are most readily explicable 
on the supposition that some homoeotic changes take place between birth and the 
adult state. Probably only a few characters are affected, and notably the anterior 
spine. 
(7) Although the ^fs exhibit backward homoeosis as compared with the $s 
there is no tendency for % parents exhibiting marked backward homoeosis to 
produce more offspring, or for $ s showing forward homoeosis to give rise to 
families having a larger proportion of $s. 
(8) The values of the fraternal and parental correlations are much below 
what would be expected on the Law of Ancestral Heredity* and accord better with 
the theory of gametic purity for the characters studied. Nevertheless the values 
of these correlations are sufficiently large to prove that the number of units in a 
primary linear meristic series is not solely due to the individual environment but 
is a character transmitted from generation to generation. 
REFERENCES. 
1894. Bateson, W. Materials for the study of Variation. London. 
1897. Badr, G. Remarks on the question of Intercalation of Vertebrae. Zool. Bull. Vol. i. p. 41. 
1898. Braus, H. Ueber die Innervation der iiaarigen Extremitaten bei Selachiern, u. s. w. 
Jen. Zeit. Bd. 31, p. 239. 
1899. . Beitrage zur Entwicklung der Muskulatur und des perijaheren Nervensystems der 
Selachier. Morph. Jahr. Bd. 27, p. 415. 
1898. Heincke, F. Naturgeschichte des Herings. Abhandl. d. deut. Seefish. Vereins. Bd. ii. 
1903. Pearson, K. On the Laws of Inheritance in Man. I. Inheritance of Physical 
Characters. Biometrika, Vol. ii. p. 357. 
1904. . Mathematical Contributions to the Theory of Evolution. XII. On a Generalized 
Theory of Alternative Inheritance, with special reference to Mendel's Laws. Phil. Trans. 
A, Vol. 203, p. 53. 
1900. PuNNETT, R. C. On the Formation of the Pelvic Plexus, etc. Phil. Trans. B, Vol. 192, 
p. 331. 
1901. . On the Composition and Variations of the Pelvic Plexus in Acanthias vulgaris. 
Proc. Roy. Soc. Vol. 69, p. 2. 
1899. RiDEWOOD, W. G. Some Observations on the Caudal Diplospondyly of Sharks. Jour. 
Linn. Soc. Vol. 27, p. 46. 
1880. Storm, V. Bidrag til Kundskab om Throndhjemsfjordens Fauna. III. Kongelige Norske 
Videnskabers Selskabs Skriffcer, 1880, pp. 73—96. Throndhjem, 1881. 
* [See footnote, p. 342. K. P.] 
